Switch for operating artificial limbs



June 9, 1953 s. w. ALDERSON SWITCH FOR OPERATING ARTIFICIAL LIMBS 15 Sheets-Sheet 1 Original Filed July 10, 1948 INVENTOR Jamaal Mfliderson.

S. W. ALDERSON SWITCH FOR OPERATING ARTIFICIAL LIMBS June 9, 1953 15 Sheets-Sheet 2 Qriginal Filed July 10, 1948 INVENTOR fl/dcrsw'z.

Samuel W BY W 6.

AGENT June 9, 1953 s. w. ALDERSON 2,640,994

SWITCH FOR OPERATING ARTIFICIAL LIMBS Original Filed July 10, 1948 I 15 Sheets-Sheet 3 ELBOW PIVOT June 9, 1953 s. w. ALDERSON 2,640,994

SWITCH FOR OPERATING ARTIFICIAL LIMBS Original Filed July 10, 1948 15 Sheets-Sheet 4 ELBOW PIVOT June 9, 1953 s. w. ALDERSON SWITCH FOR OPERATING ARTIFICIAL LIMBS 15 Sheets-Sheet 5 Original Filed July 10, 1948 S. W. ALDERSON SWITCH FOR OPERATING ARTIFICIAL LIMBS June 9, 1953 15 Sheets-Sheet 6 Original Filed July 10, 1948 INVENTOR Jamaal Wflldcnson June 9, 1953 s. w. ALDERSON SWITCH FOR OPERATING ARTIFICIAL LIMBS Original Filed July 10, 1948 INVENTOR Samuel l lf/iidcrtson.

, BY w m June 9, 1953 s. w. ALDERSON SWITCH FOR OPERATING ARTIFICIAL LIMBS Original Filed July 10, 1948 15 Sheets-Sheet 8 l NVENTOR Jamzzeillf/ilderson BY 2' %6N"f" wk vlmv & P 2 I 79 I O 3. l aw Q v5 m FQ hm wmm 3 NM w& w%

NE: SQ Q i 9 0:,

June 9, 1953 s. w. ALDERSON 2,640,994

SWITCH FOR OPERATING ARTIFICIAL LIMBS Original Filed July 10, 1948 15 Sheets-Sheet 9 INVENTOR Jamuel Wfllderson.

AGENT June 9, 1953 s. w. ALDERSON SWITCH FOR OPERATING ARTIFICIAL LIMBS l5 Sheets-Sheet 10 Original Filed July 10, 1948 INVENTOR Samuel W/Ylderfion.

AGENT m N 0E June 9, 1953 s. w. ALDERSON 2,640,994

SWITCH FOR OPERATING ARTIFICIAL LIMBS Original Filed July 10, 1948 15 Sheets-Sheet ll INVENTOR 5a m ueZ Wfl/d r June 9, 1953 s. w. ALDERSON 2,640,994

SWITCH FOR OPERATING ARTIF ICIAL LIMBS Original Filed July 10. I948 15 Sheets-Sheet 12 5a m 14 t! Wflldersarz INVENTOR June 9, 1953 s. w. ALDERSON SWITCH FOR OPERATING ARTIFICIAL LIMBS l5 Sheets-Sheet 14 Original Filed July 10, 1948 I INVENTOR Sq m :02 W'flZc/er'son l5 Sheets-Sheet 15 S. W. ALDERSON SWITCH FOR OPERATING ARTIFICIAL LIMBS INVENTOR Samuel fifllc/er so 11 .-UMk Hum il mm 6E June 9, 1953 Original Filed July 10, 1948 Patented June 9, 1953 2,640,994 swrron FOR OPERATING ARTIFICIAL LIMBS Samuel W. Alderson, New York, N. Y.

Original application July 10, 1948, Serial No. 38,018. Divided and this application May 17, 1951, Serial No. 226,881

I The present invention relates to electrically operated artificial arms cesigned for use by abovethe-elbow amputees and which may be correlated with natural arm stumps resulting from amputations and varying in length from a maximum length stump to one where the amputation occurs at or near the shoulder joint.

This application relates to subject matter found in a copending application Ser. No. 38,018, filed July 10, 1948, of which this application is a division, U. S. Patent 2,580,937. Generally speak ing, above-the-elbow amputees may be classified in two groups, one group comprising amputees who possess an upper arm stump of sufficient length and with sufficient muscular function that it may lift and guide the artificial arm naturally throughout a wide variety of positions with little or no assistance being required by extraneous body movements on the part of the amputee. The other group consists of amputees who have an extremely short stump, no stump at all, or a stump of moderate length but with impaired muscular function. These two classes of amputees may be referred to as normal and extreme cases, respectively.

The present invention in one form thereof is designed to accommodate amputees of the first group, and in another and modified form is adapted to accommodate amputees of the second group.

It is among the principal objects of the present invention to provide an electrically driven artificial arm including an upper arm section,

' a forearm section, a wrist section and a hand relative to the upper arm section; (2) hand flexion, i. e., pivotal movement of the hand section relative to the wrist section; (3) hand and wrist pronation, i. e., rotational movements of the hand I and wrist section as a unit relative to the forearm section about the longitudinal axis of the latter, and (4) opening and closing movements of the fingers which constitute a part of the hand section.

7 Claims. (01. 3-1.1)

An equally important object of the invention is to provide an artificial arm of the character outlined above in which the various relative movements of which the arm is capable of performing are accomplished solely by the power derived from a single electric motor, thus relieving nastic motions.

Another object of the invention is to provide an electrical arm capable of the above mentioned movements in which any one of them may be selectively performed without disturbing or otherwise affecting the others.

Another object of the invention is to provide an electrically driven arm of this type wherein the motive force by means of which the electrical arm is powered consists of a relatively small light-weight compact motor which is wholly contained within the forearm section of the arm in the elbow region thereof and which in the assembled arm is completely concealed from view.

Another and important object of the invention s to provide a novel type of selective clutch mechanism likewise wholly contained within the forearm section for selectively controlling by a common drive from the motor the four independent types of arm movement briefly outlined above.

A still further object of the invention is to provide an electrical arm of this type in which the selective clutch mechanism consists of a self-contained unit capable of being installed in or removed from the arm with facility as a unit and which, when installed, is mounted in the forearm section by a resilient floating connection, thereby reducing vibration and protecting the same from possible shock and, as a consequence, contributing toward the elimination of noise. A similar and related object is to provide an electrical arm in which the motor is likewise mounted within the forearm section by a resilient floating connection to further reduce vibration and it attendant noise factor. I

Yet another object of the invention is to provide an electrical arm capable of the four independent types of motion set forth above in which the motions may be reversed at the will of the amputee by the simple expedient of reversing the direction of rotation of the motor shaft while maintaining any one of the selected types of control in effect.

Still another object of the invention is to provide an electrical arm capable of the four independent motions outlined above and in which three of them, namely, the driving connections for accomplishing wrist flexion, hand and wrist pronation, and finger movements, are self-locking by a high ratio worm drive so that back thrust existing by virtue of the application of countertorque or pressure to any component movable part of the arm will not be carried throughto the selective clutch driving mechanism, thus eliminating cumbersome and expensive independent locking mechanisms which are ordinarily provided in other types of power driven artificial arms.

A specific object of the invention is to provide an electrical arm having a hand section which closely simulates the natural hand both in shape and cosmetic appearance and in which a major group of fingers comprising the index and middle fingers are opposed to the thumb and may be moved bodily in unison relative to the thumb for the purpose of grasping objects therebetween and releasing them.

Another object of the invention is to provide an artificial arm having such a hand section in which the minor group of fingers, i. e., the. ring and little fingers, are articulated in such a manner that the phalanges thereof are capable of movement relative to each other, thus permitting the fingers to assume a number of natural positions as determined by the will of the user. Accordin to the invention, these fingers have no connection with the driving motor but are merely capable of being preset to predetermined desired positions.

Another specific object of the invention is to provide an artificial arm having a hand section in which the thumb is capable of assuming a plurality of releasable but locked positions so as to cooperate with the major group of fingers in such a manner as to accommodate the grasping of relatively large objects, such as a glass or tumbler, therebetween or of relatively small objects, such as a pencil or a sheet of paper.

Another object or" the invention is to provide an artificial arm having a hand section and a wrist section, which sections are capable of continuous rotation or pronation in unison as a unit in either direction relative to the forearm, thus enabling the amputee to perform such operations, as for example, the insertion or removal of a light bulb from a lamp or wall socket, the use of a rotary tool, etc., without having to resort to oscillatory pronation and intermittent finger release as is the case with the natural hand.

Another object of the invention is to provide an artificial arm including a selective clutch mechanism, as outlined above, in which one of the clutch elements serves to efiect elbow fiexion and m which a friction lockin device is employed to prevent flexion of the forearm relative to the upper arm when the driving motor is not in the actual driving process.

Another object of the invention is to provide an artificial arm having an elbow drive train of gears together with a limit stop which cooperates with the driving train to determine the maximum amount of elbow fiexion permissible.

Another object of the invention is to provide an artificial arm including a selective clutch mechanism of the type briefly outlined above in which selection of the particular type of motion desired may be made under the control of a series of contacts adapted to be operated by relative movement of an anatomical part of the body, as for example, the big and little toes of one foot of the amputee.

Another object of the invention is to provide an electrical control for initiating energization of the driving motor and also for causing reversal of the motor under the control of the biceps muscle of the upper arm stump of the amputee or, in an extreme case where the amputee has no stump, movement of the toes on the other foot of the amputee which is not employed for efiecting selective control as outlined above. Another related object of the invention is to provide an electrical over-all control in the form of an actuator switch for rendering the selective and operational controls inoperable, such switch serving to start or stop the various movements of the ,electrical arm as required.

Another object of the invention is to provide a novel means for supporting an electrical arm on the upper arm stump or shoulder of an amputee in which the weight of the arm is distributed over widely separated points on the body of the user to alleviate the efiort required on the part of the amputee to raise or lower the arm, as well as to prevent separation of the arm from the body.

Another object of the invention in the modified form thereof is to provide an electrical arm for extreme case amputees having means associated therewith for locking the forearm section against horizontal swinging movement when the forearm is flexed less than a predetermined degree of fiexion relative to the upper arm but which will permit such swinging movement when the angle of fiexion exceeds the predetermined degree. By such an arrangement the amputee is afforded certain latitude of manipulation heretofore unattainable in conventional artificial arms.

Another object of the invention in the modified form thereof is to provide an artificial arm for extreme case amputees in which elevation of a shoulder blade will serve to raise the arm bodily as a whole. A related object of the invention is to provide an arm of this character in which horizontal swinging movements of the upper arm are effectively prevented when the arm is raised but are permitted when the arm is lowered to a pendant position in order that the extended artificial arm may swing in a. normal manner simulating that of a natural arm during the natural gait while walking.

In carrying out the above mentioned objects, very briefly, the electrical arm proper includes four main sections, namely, an upper arm or stump-receiving section, a forearm section, a wrist section and a hand section. The upper arm or stump-receiving section is hingedly secured to the forearm section by an elbow joint. The wrist section is rotatably attached to the forearm section in axial alignment therewith. And the hand section is hingedly secured to the wrist section by a wrist fiexion joint.

The hand section includes a series of fingers including a minor finger group comprising an articulated little finger and an articulated ring finger, these fingers being capable of independent movement so as to assume various convenient positions. The hand section also includes a substantially rigid mechanically movable major finger group comprising the index and middle fingers, and a substantially rigid thumb which opposes the index and middle finger group. The major finger group is capable of movement relative to the thumb to permit objects to be grasped between the fingers. The thumb is capable of being locked in either of two positions relative to the movable finger group to accommodate the grasping of objects of varying thickness. The forearm section is divided into a forearm proper and an elbow section, the latter enclosing a small electric motor and the former having disposed therein a selectively operable multiple clutch mechanism which is operatively connected to the motor and from which there extends four independent series of output gearing, one series constituting a means for affording elbow fiexion, another series constituting a means for providing continuous hand and wrist pronation, another series providing for approximately of wrist fiexion and another series providing for finger manipulation.

Suitable means are provided for attaching the upper arm section of the electrical arm to the the control of the amputee.

' 'arm mechanism,

therefor;

body power of the amputee is reserved exclusively for motions of the upper arm section.

The selective clutch mechanism referred to above is reversible in all four phases of its operation. An electrical contro1 means for selectively actuating the clutch mechanism is provided under A novel form of switch mechanism is located in one of the shoes of the user and may be manipulated by the toes for selectively operating the clutch mechanism to obtain the desired motions of the component parts of the arm. In the case of an amputee having a sufficiently long above-the-elbow stump including an active biceps, the stump section has associated therewith a stump switch adapted to be operated by a partial tensing of the stump biceps to provide a master control capable of energizing or de-energlzing the motor so that motion or no motion of the arm is effected, as

.desired. The stump switch is also used to control the direction of motion of the component parts of the arm after a selection of the type of motion desired has been made by the electrical foot controls.

To maintain the electrical arm firmly in position on the body of the user and to prevent disarticulation between the upper arm section and stump and also to equitably distribute the weight of the arm about the body of the user, a cooperating shoulder harness and pelvic support is provided. The shoulder harness is operatively connected to the upper arm section of the electrical arm by a sliding hinge connection and is also connected to the pelvic support by a semi-rigid connection so that the weight of the arm is distributed between the shoulder and pelvic regions of the amputee. The specific nature of the shoulder harness and pelvic support will be varied to satisfy the exigencies of the individual amputee, but in any case, the essential features of :the invention are at all times preserved.

In the accompanying fifteen sheets of drawings In the drawings:

Fig. 1 is a perspective view of the electrical arm proper showing the same being worn by a right-arm amputee having an upper arm stump of substantial length and also showing the harness by means of which the arm is retained on the body of the user.

Fig. 2 is a view similar to Fig. 1 showing the amputee seated and illustrating the manner in which the movements of the arm may be controlled by manipulation of the feet. In this view, the arm is shown in a raised position.

Fig. 3 is a view similar to Figs. 1 and 2 showing the linkage between the shoulder strap and the upper arm section of the electrical arm; to-

gether with the connection between the shoulder strap and the abdominal or waist belt.

Fig. 4 is a fragmentary side elevational view of the electrical arm showing the jointed sections thereof.

Fig. 5 is a fragmentary top plan view of the structure shown in Fig. 4 and including dotted 5 line illustrations of internal structure of the I I together with suitable legends Fig. 6 is a schematic view of the various drive mechanisms and clutches employed in connection with the electrical arm illustrating the manner in which the desired arm movements may be attained upon proper clutch selection.

Fig. 7 is a schematic end view of the selective clutch mechanism employed in connection with the present invention with the clutch centers in their proper positions.

Fig. 8 is a fragmentary enlarged detailed sectional view taken longitudinally through the elbow joint structure and a portion of the forearm section proper showing the electric motor, the main driving shaft and a portion of the selecting devices for the selective clutch mechanism employed in connection with the electrical arm.

Fig. 9 is a sectional View taken substantially along the line 9-9 of Fig. 8.

Fig. 10 is a sectional view taken substantially along the line l0|0 of Fig. 8. 1

Fig. 11 is a sectional view taken substantiall along the line ll-ll of Fig. 10 and showing in detail a radial clutch actuating arm employed in connection with the present invention.

Fig. 12 is a fragmentary plan view of the elbow jointv structure. In this view, portions of the outer casing have been broken away to more clearly reveal the nature of the invention.

Fig. 13 is a side elevational view of the structure shown in Fig. 12 with the casing being similarly broken away.

Fig. 14 is an end view of the structure shown in Fig. 13 with the casing broken away in parts.

Fig. 15 is an end view of the motor unit employed in connection with the present invention.

Fig. 16 is an enlarged detail sectional view taken substantially along the line |6l 6 of Fig. 8.

Fig. 17 is a sectional view taken substantially along the line l'|ll of Fig. 5.

Fig. 18 is a side elevational view of the structure shown in Fig. 17 with the casing broken away. This view shows the hand andwrist pronation drive mechanism.

Fig. 19 is a detailed sectional view of one of the clutch units proper employed in connection with the present invention.

Fig. 20 is a fragmentary view of a portion of the electrical arm in the vicinity of the wrist section thereof showing the mechanism for attaining hand fiexion and for manipulating the fingers.

Fig. 21 is a sectional view taken substantially along the line 2I2l of Fig. 20 illustrating the hand flexion and hand and wrist pronation driving mechanism.

Fig. 22 is a plan view of an inner sole employed in connection with the present invention and adapted to be worn by the amputee in his shoe for controlling a series of electrical toe contacts by means of which various movements of the arm may be attained.

Fig. 23 is a sectional View taken substantially along the line 23-43 of Fig. 22.

Fig. 24 is a sectional view taken substantially along the line 24-24 of Fig. 20.

Figs. 25, 26, 27 and 28 are fragmentary sectional views somewhat schematic in their representation illustrating the operation of a selflocking thumb construction employed in connec tion with the present invention and which is capable of being prepositioned to satisfy the preference of the user.

Fig. 29 is a sectional view taken substantially along the line 29-29 of Fig. 6.

Fig. 30 (adjacent Fig. 1) is an enlarged fragmentary view of a portion of the upper armsectionioftheelectrical arm illustrating the-manner inwhich a stump switch employed in connection with the invention may be manipulated by the biceps muscle of the amputee.

Fig. 31 is. a circuit diagram of. the. electrical connections for the arm.

Fig, 32 is a fragmentary front elevational view of a modified form of supporting mechanism for the electrical arm and designed ioruse by stumpless amputees or for amputees having, extremely short upperarm stumps.

Fig. 33. is a sectional view taken substantially along the. line 33-33 of Fig. 32.

Fig, 34. is a side elevational view of a locking deviceemployed in connection with the. modified formof the invention.

Fig. 35 (adjacent Fig. 22) is a fragmentary view similar to Fig. 22 showing a portionof an inner sole adapted to be worn by an extreme case of stumpless amputee in hisv shoe for efiectin certain electrical controls. associated with the electrical arm.

Fig. 3-6 is a circuit diagram of. the. electrical connections for. the electrical. arm when employed by an extreme case amputee.

In all of the. above described views like characters of reference are employed to designate like parts throughout.

BRIEF DESCRIPTION Referring now to the drawings in detail and in particular to Figs. 4 and 5, the electrical arm involves in its general organize" 'cn a rigid upper arm structure fragmentarily shown at it, a rigid forearm structure or assembly 52, a wrist assembly I4 and a hand assembly It. The forearm assembly l2 includes a forearm section proper l8 and an elbow joint structure or assembly 2", the latter being pivotally connected as-at 22 to the upper arm structure ID. The wrist assembly I4 is coaxial with the forearm section [3 and is pivotally connected to the free end of the latter for rotational movements in either direction about the common axis of the two sections by means of a pronation joint structure. 24 which is common to the two sections.

The wrist assembly [4 and hand assembly iii are pivotally connected together by a hand flexion joint'26. The hand assembly l6 includes. a palm portion 28.and four independently movable digit oriinger sections including a. rigid thumb 3c pivotallysecured as at 32 to the palm portion 28, a multiply articulated little finger 34, a multiply articulated ring finger 35 and separately'rnolded index? and middle fingers 38 and iorespectively, whichare'movable in unison'relative to the palm portion 28; As shown in b'ythe index,.middle, ring and little fingers are pivoted for swinging movement relativeto the palm portion 28 on a common finger pivot in the form of ,a'pintlepin 62.

Still. referring to Figs; 4 and 5, and also to Figs. 1-2 and 13, the upper arm structure includes'a pair of spaced parallel structural members 44 and 46 which are pivotally' attached by means of the connection. 22 to the elbow joint structureifl: and which serve to support therebetween a tubular stump-receiving socket or casinglii' (see also Figs. 1, 2, 3 and. 30). The elbow joint structure 2G is in the. form of a casting 2i having a removable cover 23 and which contains the electric motor M (Fig. 8) by means of. which all the operative movable instrumentalitlescomprising the electrical arm are selectively driven at the. will of theamputee. This structure also contains certaingear reduction mechanismand the gearing by means of whiohelbow nexion takes place and which will be described in detail sub sequently.

The forearm section proper l8 involves in its general organization a forearm frameworkdesi'gnated in its entirety at 50 (Figs. 17 and 18) which serves to support thereon a pair of forearm covers. 52 and 54 which may be of a sound-proof nature and which serve to enclose various clutch and gearing mechanisms, as well as certain electrical instrumentalities, the nature of which will be fully described hereinafter.

The. pronation joint structure 24 in the main is in. the form of a bearing member having counterparts associated with both the forearm section proper l8 and the wrist assembly [4. The wrist assembly His in the form ofa tubular cosmetic shell or casing 56 and within this casing there are disposed certain hand fiexion driving mechanism, as well as the pivotal connection for the palm portion 28. A train of driving mechanism leading from the motor M. to the major'finger group 38, also passes through the wrist shell 56.

The palm portion 28' is in the form of a twopiece separable cosmetic shell 58, 59 in which is disposed the immediate finger driving instrumentalities, including the pivotal connections 82, 42 for the various fingers of the hand. The thumb 30 is in the form of a hollow molded cosmetic shell, as are both the index and middle fingers which operate in unison. The little and ring fingers 35, 36 are of an articulated type andare designed for independent positional movements and the nature of these fingers will be set forth subsequently.

A shoulder harnessis designated in its entirety at (Fig. 3) and has flexible connections with the upper arm structure 10 which prevents separation between the stump and stump-receiving socket 48 and a semi-rigid connection-with a pelvic suspension device 65. The shoulder harness 60 and pelvic suspension deviceBS, together with the connections between them, serve to distribute the entire weight of the electrical arm-between the shoulder and pelvic regions of the amputee.

The electrical arm is poweredby meanso! a small, compact; portable battery unit B (Figs. 2 and 31) adapted tooe conveniently'carriod inthe trousers pocket 68, preferably on the same side as the amputation. The control. or" the; various movements of the electrical arm. is eflected by means of a series of electrical contacts contained in one of the shoes of the. user, as for example, the right shoe TO, and also'under the controlof a stumpswitch assembly [2 (Figs. 1, 2, 30 and 3l). The control contacts in the. shoe areutilized for the purpose of effecting the selected'type of movement for the various parts of the. arm, while the stump switch is employed to initiate the selected type of movement as well as for selecting aforward or reverse movement, all in a manner that will be made clear presently.

THEMOTOR, MOTQR. DRIVE AND SUPPORT- ING STRUCTURE THEREFOR Referring now to. Figs; 8,12,.13, l4 and'l5,rthe motor M, whichls of. the direct current, reversible, permanent magnettype, is supported within the elbow joint structure by means of a resilient floating connection. The elbow joint structure 20 includes a base casting 21 which is of boxlike configuration and which has an open upper end adapted to be. closed by means of a cover plate. 23. The forward end of. the elbow joint structure is provided with a rectangular channel portion 18 afiording an external groove adapted to receive therein a suitable sealing gasket 82 (Figs. 8 and 13) which may be formed of soft rubber or the like, and which affords a seal for the forearm section proper I8 when the cover plates 52 and 54 are in position.

The motor M is in the form of a substantially rectangular box-like casing which is bolted or otherwise secured as at 86 to a gear reduction assembly 88, likewise of box-like configuration, and which is mounted by means of a floating connection from the casting 2I. The floating connection just referred to includes an upstanding bracket 90 which is secured to the end wall 92 of the casting 2I by means of through-bolts 94 and which is spaced therefrom by means of spacing collars 96. A plurality of attachment plates 98 are secured to the bracket 90 by means of studs I and these attachment plates 98 are fastened to respective supporting pads I02 which may be formed of resilient material such as rubher. The supporting pads I02 are fastened to respective attachment bosses I04 carried on the casing of the gear reduction assembly 88 and thus the gear reduction device and the motor are yieldingly supported from the casting 2I with the solid resilient pads I02 constituting the sole supporting means for the motor and gear reduction assembly.

The gear reduction device 68 is provided with an output shaft I06 which is connected through a resilient coupling I08 to a floating shaft IIO which in turn is connected through a second resilient coupling I I2 to a shaft I I4, which may be regarded as the main drive shaft leading to the various gear train mechanisms employed for effecting the desired movements of the component parts of the electrical arm.

THE SELECTIVE CLUTCH ASSEMBLY Referring now to Figs. 6, '7, 8, 9, 12, 13, 17, 18 and 19, the selective clutch mechanism is designated in its entirety at I 20 in Figs. 17 and 18, and is a. unitary self-contained assembly which is mounted within the forearm section proper I 8 by means of a floating connection. The drive shaft II4 constitutes the input drive for this clutch assembly.

The clutch assembly involves in its general organization a rigid but floating frame-like structure I 22 including a front end plate I24 (Fig. 6 and 18) a medial plate I26 and a rear end plate I28 (Figs. 10 and 12). The plates I24 and I26 are connected together by means of spacing members I38 and the medial plate I26 and end plate I28 are connected together by means of spacing members I32. The end plate I24 is provided with a pair of laterally extending ears I34 which are supported from a pair of longitudinal- 1y extending parallel frame members I36 and I 38 integrally formed with an end piece in the form of a ring I constituting a part of the forearm framework 50. The frame members I36 and I38 are generally of channel-shaped construction to lend strength to the structure and they may be integrally cast with one element of the pronation joint structure 24 at the front of the forearm section proper IB. At the rear of the forearm section the members I36 and I36 are secured toa pair of block members I40 and I42 respectively, and these block members in turn are secured to the inner surface of the elbow joint structure 20 on opposite sides thereof and thus the members I36 and I38 serve to maintain the pronation joint structure 24 spaced from the forward end of the elbow joint structure 20.

The clutch mechanism proper I20 includes a series of four clutch elements I 44, I46, I48 and I50. The clutch element I44 is adapted to go into operation to effect the elbow drive or, in other words, to attain elbow flexion. The clutch I 46 is adapted to go into operation to effect hand and wrist pronation at the pronation joint 24. The clutch I48 is adapted to go into operation to effect opening and closing movements of the index and ring finger assembly relative to the thumb. The clutch I50 is adapted to go into operation to effect hand flexion, all in a manner that will presently be set forth.

The clutch elements I44, I46, I40 and I50 are substantially identical in construction and are mounted in the floating clutch assembly I22 at substantially equally spaced points arranged about a common center and these elements occupy the same transverse plane.

Each clutch element includes a supporting shaft I52 which is rotatably journaled in the front and medial plates- I24 and I26. The clutch elements are of the reverse acting type, that is to say, the driven element of the clutch may coact with the driving element thereof to effect rotation of the clutch elements in opposite directions to reverse which ever character of motion of the electrical arm is selected. A driven element I54 is mounted upon and secured to the shaft I52. This element is in the form of a aircular disc having outwardly projecting clutch teeth I56 on one side thereof. These teeth OI pose a series of similar teeth provided on the driving element I58 of the clutch. The driving element is similar in configuration to the driven element and is rotatably mounted on the shaft I52 in close proximity to the driven element. Each driving element includes an integrally formed gear I60 and all four of the: gears I60 are in constant mesh with an idler gear I62 mounted on a shaft I63 rotatably journaled in the front and medial plates I 24, I26. The gear I60, which is integrally formed with the clutch I 48 and which controls the opening and closing movements of the fingers, meshes with a driving gear I65 mounted on the drive shaft H4 and thus when the motor is energized and the drive shaft H4 is rotated, a drive is transmitted from the gear I65 to the gear I60 of the clutch I48 and from thence through the idler gear I62 to all of the clutch elements I58 so that these elements rotate in unison.

When the arm. is at rest and no relative motion between any of the component parts thereof is contemplated, the drive shaft I I 4 remains stationary due to lack of energization of the motor M. As soon as a selected movement of the arm is contemplated, the motor M is energized by means of a suitable control to be described subsequently and the drive shaft II4 commences to rotate in the selected. direction, thus causing all four of the driving gears I60, and consequently all four of the driving elements I58, to rotate in unison. Until one of the clutches I44, I46, I46 or I50, as the case may be, is thrown into meshing engagement no movement of any parts of the arm will result and when the selected clutch is finally engaged one of the four types of movement, namely, opening and closing of the fingers, hand and wrist pronation, hand flexiorn or elbow flexion, is attained. In Fig. 6 the various drives for effecting these motions is schematically shown.

Each shaft I52 is slidably, as well as rotatably, mounted in the front and medial plates I24, I26 

